Printing machine



Dec. 9, 1958 Filed March 31, 1955 C. R. JOHNSON PRINTING MACHINE 2Sheets-Sheet 1 aza-dliJoizmo 5 Mam fliioflrzeg;

Dec. 9, 1958 Filed March 31, 1955 C. R. JOHNSON PRINTING MACHINE 2Sheets-Sheet 2 Inversionazz' R. JOWOW, AM; 0 M

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ul atented Dec. 9, 1958 PRINTING: MACHINE Carl R. Johnson, Keene, N;l-I.,assiguo'r to I A. Putnam Mfg. C0., lnc., Keene; N. -ll-l., acorporation of New Hampshire Application March 31, 1955, Serial No.498,145

3 Claims. (Cl. 101-426) This invention relates to printing. machines ofthat type which use a stencil fonmaking the imprint, and especiallystencils that aresupported on a screen of some suitable material such assilk, nylon, linen, glass fibre, metal, etc., and which may. forconvenience be referred to as screen stencils, although the invention isnot limited to stencils of this character but may be used with stencilsof other types.

A method now commonly used for making imprints with a screen stencilinvolves placingthe screen stencil in contact with the work piece onwhich the imprint is to be made and then forcing the ink through thescreen stencil by a squeegee operation. This squeegee method of making asuccession of imprints has a disadvantage that it isa rather slowprocess.

Another known method of making imprints with a stencil is by means of aprinting machine of the type having a printing head carrying aninkreservoir containing ink, the bottom of which is constituted by animprint forming stencil, and which is movable into and out of printingposition so at each movement of the printing bead into printing positionan imprint willbe made.

This type of printing machine is sometimes provided with means tosubject the ink in the reservoir to pressure when the stencil is broughtinto printing position thereby to force the ink through the stencil tomake the imprint.

This operation of bringing the screen stencil against the work piece andsubjecting the ink in the reservoir to the desired pressure and thenseparating the ink reservoir from the work piece occupies a space oftime much less than that occupied by the ordinary squeegee operation forforcing the ink through the stencil to make the imprint.

One object of the present invention is to provide novel means forsubjecting the ink in the reservoir to the desired pressure at the timethat the imprint is being made.

In the drawings which show one embodimentof the mventlon;

Fig. 1 is a side view of a printing machine equipped with the newprinting unit;

Fig. 2 shows one form of printing unit in section;

Fig. 3 is a detail of one means for controlling the pressure on the inkin the reservoir.

Fig. 4 is a sectional view showing a different embodiment of theinvention;

Fig. 5 is a fragmentary view of means for. controlling the pressure onthe ink in the device shown in Fig. 4.

In Fig. lthe invention is shown as embodied in a well known type ofprinting machine having a frame It carrying a work support 2 and havingthe printing head mounted in a vertically reciprocating member 3 whichis movable toward and from the work support 2. As herein shown, themember 3 is in the form of an arm pivoted to the frame 1 at 4, and itreceives an upand down movement through the medium of a toggle membercomprising the two toggle arms 5 and 6 which are pivotally connectedtogether at 7, the arm 5 being pivoted. at its upper end to the frame 1at 8, and the lower end of the arm 6 being pivoted to the member 3 at 9.The up and down movement of the arm 3 is produced by breaking andstraightening the toggle member 5, 6. When the toggle member is broken,the member 3 is in its raised position, as shown in full lines Fig. l,and when said toggle member is straightened the member 3 carrying theprinting element is in its lowered printing position as shown in dottedlines. This operation of making and breaking the toggle may be providedfor by any suitable means, such, for instance, as a crank disk 10carried by a drive shaft 11 and having a crank pin 12 which is connectedby the link 13 to the joint 7 of the toggle lever member. The rotationof the crank disk 10 will give the toggle member its breaking andstraightening movement, as will be clearlyunderstood.

Printing machines of this type are in common use and the construction asthus far described forms no part of the present invention.

in embodying the present invention in a printing machine of this type,the printing head is provided with a reservoir 14 containing the inkused for making the imprint, which reservoir may be mounted on themember 3, the lower end of the reservoir being constituted by thestencil 15, which may be a screen stencil or a stencil of any othersuitable type.

One feature of thepresent invention relates to means for subjecting theink 16 in the reservoir 14 to pressure at the time that the stencil i5is in contact with the work piece, thereby forcing the ink through thestencil onto the work piece 13 which is supported bythe work support 2,thereby to make theimprint.

in the construction shown in Figs. 1 and 2 the ink reservoir it has aplunger l7 located therewithin which rests on the ink is, and means areemployed for applying a momentary downward pressure to the plunger atthe time when .the 'screen stencil is brought against the work piece,thereby subjecting .the ink in the reservoir to the necessary pressureto force a sufficient quantity thereof through the screen to make aproper imprint.

One means of accomplishing this is to provide an air cylinder 19 whichis mounted on top of the reservoir 14 and to provide a piston 24 withinthe air cylinder having a piston rod 21 which extends through the top ofthe reservoir 14 and is connected to the plunger 17, and also to providemeans for subjecting the piston 20 to a momentary downward pressure atthe instant that the screen stencil has been brought against the workpiece 18. This may be accomplished in various ways, and for the purposeof illustration there is shown herein a pneumatic means to accomplishthis end. The upper end of the air cylinder 19 has an air supply pipe 22connected thereto above the piston Zti, which. pipe is supplied with airunder pressure fromany suitable source. Located in the pipe 22 is avalve 23 of a well known type which is constructed so that normally itcloses the communication between the cylinder and the source ofcompressed air supply and vents the upper end of the cylinder 19 to theatmosphere, but whichwhen actuated closes the vent and opens momentarilythe cylinder to the pipe 2.2, thereby admitting compressed air to thecylinder above the piston 2h, whereby said piston is subjected to adownward pressure which is transferred to the plunger 17 through thepiston rod 21 and thus to the ink in the reservoir. While the valve 23may be operated in any desired way, a construction is herein shown bywhich this valve is operated electrically through the medium of acontrol switch 24 mounted on the frame 1. This control switch isnormally open and, assuming the to make the imprint on the work piece.

valve 23 is a solenoid operated valve, said valve will thus normally bein a condition to vent the upper end of the air cylinder 19 and closethe pipe 22. leading to the source of compressed air supply. The crankdisk iltt is provided with'a cam portion 25' which is positioned toactuate the switch member 24 at the time that the screen stencil hasbeen brought into contact with the work piece 18. The closing of theswitch 24 activates the solenoid valve 23 so that the upper end of thecylinder is placed momentarily in communication with the source ofcompressed air through the air pipe 22, and an impulse of compressed airwill be thus delivered to the cylinder 19 above the piston 26 which willapply downward pressure to the piston 28* and thus subject the ink 16 inthe reservoir to a momentary increased pressure which will forcesufficient ink through the screen stencil As soon as the cam portion 23passes out of engagement with Lu switch 24 the valve 23 will resume itsnormal condition I in which it blocks the air flow from the air pipe 22into the cylinder and opens a vent for venting the cylinder.

The contact of the screen stencil 15 against the work piece is amomentary contact only and the present invention provides means wherebyjust at the time the screen I stencil is about to be separated from thework piece after the imprint has been made, the ink within the reservoirwill be subject to a momentary negative pressure, thus assisting thebreaking of the ink in the stencil from the imprint and producing anexceptionally clear imprint. In the construction herein shown this isaccomplished by providing a second air pipe 27 leading from the sourceof compressed air to the bottom of the cyinder '19 below the piston andemploying a second solenoid valve 28 for controlling the flow ofcompressed air into the cylinder 19 below the piston 20 through the pipe27 which communicates with a source of compressed air. This valve 28 iscontrolled by another switch 29 similar to the switch 24, and saidswitch 29 is controlled by the cam projection carried by the crank diskit).

The cam projection 25 is so positioned on the cam disk 10 that it willactuate the switch 24 just as the printing head has been moved into itsprinting position with the screen stencil 15 in contact with the work,thereby to actuate the valve 23 so that compressed air will be deliveredto the cylinder 19 above the piston 2t), whereby said piston 2d and theink 16 in the reservoir will be subjected to pressure by the plunger 17thereby to force ink through the screen stencil onto the work for makingthe imprint. As soon as cam projection 25 has passed by the switch 24,the latter will resume its normally open condition, andthe valve 23 willalso resume its normal condition in which it vents the upper end of thecylinder 19 to the atmosphere and closes the pipe leading to the sourceof compressed air.

Immediately after the crank disk 10 has moved forwardly to withdraw thecam projection 25 from the switch '24, said projection will engage andoperate the switch 29, as shown in dotted lines Fig. 3, so that thevalve 28 will be actuated to admit compressed air to the cylinder 19beneath the piston 20, thereby producing an upward impulse to theplunger 1'7 and producing a negative pressure within the ink reservoirwhich will result in quick breaking of the ink between the screenstencil and the work piece as the printing head begins its backwardmovement. When the cam projection 25 passes by the switch 29, saidswitch will resume its normally open condition and valve 28 will alsoresume its normal condition in which it vents the lower end of thecylinder 19 to the atmosphere and closes the pipe 27 leading to thesource or" compressed air.

In Fig. 4- there is shown another embodiment of the .invention in whichthe plunger 17 is omitted and the compressed air is delivered into theupper end of the j reservoir and thus applies pressure directly to theink. In this embodiment the reservoir is indicated at Ma and the inktherein at 16a, the lower end of the reservoir being constituted by thestencil 15a. For producing the increased pressure on the ink thecompressed air is delivered directly into the upper end of the reservoir14a. The delivery of such compressed air into the reservoir at theproper time and the subsequent venting of the reservoir may becontrolled by a valve 30, which is shown as a plug valve having a valvecase 31 and a valve plug 32 within the case and capable of turningmovement. The valve is connected to the top of the reservoir by a pipeconnection 33 and also has a compressed air supply pipe 34 leading tothe interior of the valve casing. The valve plug has a recess or port 35which in one position of the plug connects the pipe 33 with a vent 36and in another position connects the pipe 33 with the supply pipe 34.Any suitable means may be provided for operating the valve plug. Asillustrated in Figs -t and 5, the valve plug 32 is provided with anactuating arm 37 by which it can be turned to bring the pipe 33 eitherinto communication with the supply pipe 34 as shown in Fig. 4 or intoposition to connect the pipe 33 with the vent 36. This arm 37 is shownas acted upon by a pulling spring 39 which normally holds it in thedotted line position, Fig. 5, in which position the port 35 forms acommunication between the pipe 33 and the vent 36.

The arm 37 may be turned from the dotted line position Fig. 5 into thefull line position (dotted line position Fig. 4) by means of an arm orprojection 40 which may be mounted on the crank disk 10 or any othersuitable rotating part carried by the shaft 11. The arm 40 will be sopositioned that it engages the valve arm 37 at the correct point in theoperation of the printing machine to supply the air pressure to thereservoir 14a at the required time.

The reservoir or cylinder 14 may be secured to the vertically movingpart 3 of the marking machine in any proper way. As herein illustrated,the lower end of the cylinder 14 projects through an opening in themember 3 and said cylinder is secured to the member 3 by a collar 50which may be welded or otherwise secured to the cylinder and the member3.

The screen stencil 15 may be secured to the lower end of the cylinder 14in any suitable fashion. As illustrated, said cylinder has at its lowerend an annular lip 30 which inclines inwardly toward the bottom thereof,and the screen stencil 15 spans the opening defined by the lip 30 andthe edge 31 of the stencil is clamped to the outside of the lip 30 by aclamping ring 32 which is secured to the bottom of the cylinder 14 bymeans of suitable screws 33.

While the ink reservoir with the screen stencil forming one wall thereofis herein illustrated as in the form of a cylinder with the screenstencil forming the bottom of the cylinder, and is also illustrated asbeing mounted on a vertically moving part of a marking machine, yet itis to be understood that the particular shape of the ink reservoir andthe manner of operation of the machine to bring the screen stencil andthe work into contact for making the imprint may be varied in many wayswithout departing from the inventive idea covered by the claims.

The timing of the operation of the valves 23 and 28 and also of thevalve 30 may be varied relative to the movement of the printing headtoward and from the work support so that the pressure may be applied tothe ink either just before the printing head is brought into contactwith the work or just at the instant of such contact, or immediatelythereafter. Such timing, of course, depends upon the position of the cam25 on the crank 10, and this position may be varied to obtain thedesired result. Similarly, the moment during the operation of 'themachine at which the ink is subjected to negative pressure may be variedby proper adjustment of the switch 29.

Moreover, if it is desired to submit the ink in the res ervoir to morethan one pressure impulse, this may be accomplished by properarrangement of valves and switches for operating them, the basic featureof the invention being means for subjecting at the proper time the inkin the reservoir to pressure to force it through the stencil for makingthe imprint.

I claim:

1. A printing machine comprising a work support to support a work piece,a printing head havingan ink reservoir adapted to contain ink, thebottom of said reservoir being constituted by an imprint formingstencil, a plunger in the ink reservoir resting on the ink therein, anair cylinder mounted on and located above the reservoir, a piston insaid cylinder, a piston rod connecting the piston and plunger andextending through the top of the reservoir, printing head moving meansto move the printing head into and out of printing position, meansactuated by the printing head moving means as the stencil is making animprint to admit momentarily compressed air to the cylinder above thepiston, thereby to subject the piston and the plunger to downwardpressure to force ink through the stencil, and immediately thereafter toadmit compressed air into the cylinder below the piston, thereby tosubject said piston and plunger to an upward impulsio-n to efiect aquick breaking from the work piece after the imprint has been made.

2. A printing machine comprising a work support to support a work piece,a printing head having an ink reservoir adapted to contain ink, thebottom of said reservoir being constituted by an imprint formingstencil, a plunger in the ink reservoir resting on the ink therein, anair cylinder mounted on and located above the reservoir, a piston insaid cylinder, a piston rod connecting the piston and the plunger andextending through the top of the reservoir, printing head moving meansto move the printing head into and out of printing position, an uppercompressed air supply pipe leading to the cylinder above the piston, alower compressed air supply pipe leading to the cylinder below thepiston, a normally closed valve in each supply pipe, means renderedoperative by the printing head moving means as the stencil is broughtinto printing position to open momentarily the valve in the uppercompressed air supply pipe to admit air to the cylinder above thepiston, thereby to produce a downward pressure against the piston andplunger to force ink through the stencil, and as the printing headstarts its return movement to open the valve in the lower compressed airsupply pipe thereby to admit compressed air to the cylinder beneath thepiston thereby to give the piston and plunger an upward impulsion toeffect a quick breaking of the ink from the work piece after the imprinthas been made.

3. A printing machine as defined in claim 2 in which the means foroperating the two valves is a crank disk rotating in timed relation withthe movement of the printing head and having a single cam projection onits periphery, and in which said two valves: are situated closelytogether with a portion of each valve in the path of the cam projectionas the crank disk rotates and with said portions placed so as to beengaged by the cam projection successively.

References Cited in the file of this patent UNITED STATES PATENTS

